1. Field of the Invention
The invention relates to apparatus and methods for controlling equipment and to a message packet for use with such apparatus and methods.
2. Description of the Prior Art
As equipment becomes more and more complex, it becomes progressively more difficult to provide a user interface for controlling the equipment. One example of the difficulties which can be encountered is where it is desired to control a number of different pieces of equipment by a common control unit. Ensuring compatibility of a control unit and the controlled equipment is difficult because the different pieces of equipment to be controlled may carry out different functions and/or have different control requirements. Also, even if the equipment to be controlled is essentially the same, differences in the model or version of that equipment may give rise to incompatibility.
Another area where the complexity of control is experienced is during the development of new equipment. Complex equipment typically requires a complex control hierarchy. At the lowest level of the hierarchy are hardware devices carrying out basic functions. Overlying this level there is typically provided a level of control in the form of a hardware interface for controlling the hardware. Above this level a user interface enables the user to interface with the hardware interface and ultimately with the hardware devices. Typically, the hardware interface and the user interface levels are at least partially implemented in software. Often the software for the user interface and for the hardware interface can take as long, if not longer, than the hardware to develop. Moreover, development of the user interface and the hardware interface can often be performed by different development team and/or the development of these stages is staggered. As a result of this, any small change to the hardware level or the hardware interface level can mean that a resulting change has to be made to the user interface level. To avoid errors occurring, it is important that the user interface is compatible with and has the same development level as the hardware interface and the hardware. It will be appreciated that this can cause difficulties, particularly in an example as described above where it is desired to use a common control unit for controlling different pieces of controllable equipment.
Apparatus has been proposed in which, in order to ensure compatibility between a control unit and a controllable piece of equipment, the hardware interface of the controllable equipment is effectively duplicated in the separate control unit. This means that the control unit is dedicated to the controllable equipment with the result that this arrangement is inflexible and requires significant development in order to ensure full compatibility.